Combustion control



July 30, 1929.

J. C. GIBSON COMBUSTION CONTROL Filed June 25, 1927 2 Sheets-Sheet 1 y30, 1929- J. c. GIBSON 1,722,415

COMBUSTION CONTROL Filed June 25, 1927 2 Sheets-Sheet 2 T720672 firfijjraon C 6507;

. Patented July 30, 19 29.

I UNITED STATES PATENT oar-lea mrnnson c; (mason, or cnrcaeo, rumors.

COMBUSTION CONTROL.

Application filed June 25,

properly. The combustion chamber becomes filled with an accumulation ofexplosive gases whichcannot be carried off by the cold stack and if thegases are then ignited, a disastrous explosion is liable to occur.

In this invention,- a time element circuit breaker is incorporated inthe combustion or stack thermostat, which in itself is a safety control,in such manner that the stack thermostat switch ispermanently openedwhen the system does not function properly. After the switch has beenopened, it requires manual restoration, so that attention is called tothe faulty operation of the furnace.

The main objects of the present invention are to provide a simple,rellable safety combustion control system; to provide a combustioncontrol in which the stack thermostat switch is utilized for the timeelement circuit breaker; to provide an adjustable circuit breaker. whichmay be ad'usted to suit the operation of the particuiar furnace withwhich the control is used; to provide a control in which the stackthermostat is, also utilized for controllin' the ignition; to pro- ,videa control in w 'ch. both the motor circuit and the ignition circuit areopened by the same safety device; and to provide a simple form of anadjustable single acting circuit breaker for a combustioncontrolsystern. 1

Anillustrative embodiment of this invention is shown in the accompanyingdraw: ing's, in which: Figure 1 is a diagrammatic illustration of theautomatically controlled combustion system.

- Fig. 2 is a plan section through the stack, showing an outside view ofthe stack thermostat. I

Fig. 3 is a face view of the stack thermostat with the cover' removed.

Fig. 4 is a view of the stack thermostat with the housing shown insection and the 1927. Serial No. 201,418.

switch arm rotated into the vertical position for the purpose ofillustration Fig. 5 is a. detailed section taken on the line 5-5 of Fig.3.

Fig. 6 is a view of the upper portion of the parts shown in Fig. 3showing the switch 1n the dropped position.

In this invention, the mercury switch bulb of. the stack thermostat ispivotally mounted on the thermostat switch arm, and is releasably heldthereonin normal position. The

switch bulb is released so that one end drops down by an emergencyoperation of an electro thermal device comprising a bi-metallic barwhich is heated by means of a resistance 'coil placed in series in thestartingrcircuits.

Referring to the drawings in ig. 1, a furnace 7 is provided with aburner 8, which is operated by the motor 9 for supplying the fuel andair requisite for supporting the combustion. When the burner is started,

the fuel mixture is ignited by means of a spark gap device 10 which issupplied with high tensioned current from the transformer 11.

The combustion or stack thermostat 12 is mounted in the stack 13, andhas a mercury switch bulb 14. The bulb is provided with three contactpoints 15,- 16 and 17, at one end, and with two points, 18 and 19, atthe other end, as is more clearly shown in Fig. 3. The first threecontacts are electrically connected by the mercury globule when theswitch arm is in the normal or cold position, in which position the bulbis inclined to the left; and the two points at the opposite end areconnected when the switch arm is in the running or hot POSI- tion inwhich the bulb is inclined to the ri ht, as shown in dotted lines in Fi3.

be room thermostat 20 is provi ed with a switch 21 which is closed atlow room temperatures. One side of the switch 21 is connected to onepole of the current supply switch 22, and the opposite side of e switch21 is connected by means of the wire 23 to the contact 19. A branch wire24 leads from the wire 23 to the electrothennal circuit breaking element25, which is then "connected by the wire 26 to the contact It, with theresult that the room thermostat is connected to both sides of theswitch. Contacts 17 and 18, which are likewise at the opposite sides ofthe switch, are oined and connected by the wire 27 to the switch 28 ofthe boiler thermostat 29; and from the switch 2 8 by means of the wire30 to one terminal ofthe motor 9. The opposite terminal of the motor isconnected by the wire 31 to the opposite side of the supply switch 22.Then the primary winding 32 of the transformer 11 is connected from thesupply Wire31 to the one end contact 15 'by means of the conductor 33. p

In the cold position, the three contacts at the left'are connected, andwhen the room thermostat switch 21 is closed, the starting circuits arecompleted. Connection is made from the supply switch through the roomthermostat wire 23, through the branch 24, the heating element 25 to thecontact '16. From this contact,-'a complete connection is made throughthe boiler thermostat and the motor by means of the wires 27, 30 and 31,and also a complete connection through the primary coil of thetransformer 11 by means of the wire 33. The igniter will then beenergized to ignite the fuel mixture, and the motor 9 put into operationto supply the same. As will be described hereinafter, the heating coil25 is effective for releasing the switch bulb 14 so that all circuitcompleting connections" are opened after the coil has been in thestarting circuit a predetermined period of time. If the combustionstarts properly, the switch rod of'the stack thermostat will be rotatedso that the bulb is inclined to the right before the safety time periodhas elapsed and before the switch has been opened by the heat from thecoil 25.

The circuits, after the'stack thermostat has operated, are then in therunning condition in which the roointhermostat is still connected inseries-with the ,boiler thermostat and the motor 9, but with the igniterdisconnected.

The stack thermostat comprises a housing 36 which is provided with aremovable cover 3? and a boss 38 on the inner side, which pro ects intoan opening in the stack 13 when the thermostat is mounted in position. Abi-metallic coil 39 is anchored at one end to the'boss 38, and issecured at the outer end to the rod 40.

The rod 40 is rotatably mounted in the boss 38 and carries, on the endwhich projects into the housing, the switch arm 41.

The switch arm is rotatable on the rod'and 1s frictionally connectedthereto by means of the spring'42-which is coiled around the rod andpressed between the switch arm and the adjusting nut 43, whichisthreadedon the endfof'the rod, to presslthe switch arm against theshoulder provided by the nut 44 w ich is also threaded on the rod 40. is

The switch arm projects at either side from thel mounting on the rod,and the lower end engages'the stops provided by the posts 45 which arefixed in the housin 36. The bi-metallic coil 39 may twist ineitherdirection throu h a greater are than the permissible are 0 movement ofthe switch through The mercury switch bulb is gripped in a clip 46 whichis pivoted on the post 47 which is rlgidly secured to the upper end ofthe switch arm. The clip carries a weight 48 at one side for rotatingthe clip and bulb counterclockwise to the off position shown in Fig. 6.Under normal operating conditions, the bulb is held in transverserelation to 'the switch arm by means of the pin 49 in the end of thebi-meta llic bar 50.

The bar 50 is anchored at the lower end to the lower end of the switcharm and slidably engages with the post 47. The clip is provided with anarcuate portion 51 having an aperture '52 into which the pin 49 isengaged to hold the bulb from turning. In restoring the switch, thebulb' is merely lifted at one end and the pin enters the ,hole as soonas it is'registered therewith.

The electrical heating element 25 is clamped between mica strips 53which are clamped to the midportion of the bar 50 by theclamp 54. Thearrangement is suchthat I when the bar 50 is heated by the element25, itis flexed so that the upper end is moved outwardly to retract the pin 49from the aperture 52 to release the switch bulb. p

This outward movement is resiliently opposed by the spring 55 which iscoiled around the post 47 and seats on the adjusting nut 56 which isthreaded on the outer end of the post. By adjusting-the nut 56 theperiod of time in which the starting ourrent-flowing through heatingelement will flex the bar to release the switch may be determined.

,VVhile but one specific embodiment of this invention has been hereinshown and described, it will be understood that details of theconstruction shown may be altered or omitted without departing from thespirit of this invention as defined by the following claims: Y

I claim: I 1. A thermostatic control instrument having an arm movablyresponsive to tempera ture changes, a mercury bulb switch'mounted onsaid arm and releasably held in fixed position thereon, andelectrothermal means mounted on the arm for releasing said switch, saidswitch being normally urged to an open position: i v. 2. Athermostaticcontrol instrument having an arm movably responsive tochanges in temperature, a mercury'switch bulb pivotally mounted on'thearm, a catch for holding the bulb in a fixed but unbalanced posi-' tionon the arm, and electrothermal means for moving the catch to release thebulb.

v 3. A thermostatic control instrument having an arm movably responsiveto changesin temperature, a mercury switch bulb pivotally mounted on thearm, a flexible member anchored to the arm and engaged with the switchbulb to hold the bulb in normal position on the arm, and an electricheating element for flexing said member to disengage the same from theswitch bulb, said bulb being normally urged to an open position.

4'. A thermostatic control instrument having an arm movably responsiveto changes in temperature, a clip for carrying a mercury switch bulbpivotally mounted on the arm, a bi-metallic bar anchored to the arm atone end and engaged with the clip at the free end to hold the switchbulb in fixed position on said arm, an electric heating element forflexing the bar to disengage from the clip, and an adjustably tensionedspring for opposing said flexing to regulate the timing, said bulb beingnormally urged to an open position.

5. A thermostatic control instrument having an arm movably responsive tochanges in temperature, a post fixed on said arm, a mercury switch bulbhaving a clip pivoted on said post, a bi-m'etallic bar anchored at oneend to the arm and engaged at the other end with the clip to hold theclip from turning on the post, an adjustable coil spring on the postpressing the bar into engagement with the clip, and an electric heatingelement mounted on the bar to flex the same against the tension of saidspring to disengage from the clip, said bulb being normally urged to anopen position.

6. In a stack thermostat having a bimetallic member in the stackconnected to a pivotally mounted switch arm for controlling the rotativeposition thereof, a mercury switch bulb having a clip pivotally mountedon the arm, said clip having a segmental portion, a bi-metallic baranchored at one end to the switch arm and having a pin at the movableend for engaging the clip to hold the switch bulb in normal position onthe arm, the pin being adapted to ride on the segmental portion of theclip when disengaged from holding the clip.

7. A thermostatically controlled instrument having an arm movablyresponsive to temperature changes, a switch mounted on said arm andarranged to be opened and closed according to the position of said arm,and electro-thermal means mounted on said arm and arranged toindependently operate said switch.

S7igned at Chicago this 18th day of May, 192

JEFFERSON O. GIBSON.

